1. Field of the Invention
The present invention relates to a method for manufacturing semiconductor devices, semiconductor devices, and electronic appliances.
2. Description of the Related Art
Heretofore, various insulating materials have been used for semiconductor devices such as display devices. In semiconductor devices, an insulating material is used so as to serve as insulating layers in many cases, and the insulating layers have a wide variety of functions. For example, for a gate insulating layer of a transistor, a function of ensuring insulation between a gate electrode and a semiconductor layer is required. Further, for an interlayer insulating layer, a function of keeping planarity of a surface may be required in addition to a function of ensuring insulation between layers. Further, for an insulating layer serving as a passivation film, a function of preventing an impurity from intruding a semiconductor layer is required.
As described above, since various functions are required for insulating layers, characteristics significantly differ between insulating layers. For example, it can be said that in the case of using an insulating layer as an interlayer insulating layer, a low dielectric constant and low hygroscopicity are required as well as a high dielectric strength voltage. A low dielectric constant is required here for enabling higher speed operation by reduction in capacitance between wirings. Further, low hygroscopicity is required for holding reliability of a semiconductor device by preventing expansion of the insulating layer due to moisture absorption to ensure planarity of a surface, thereof.
For such an insulating layer, an inorganic material containing silicon is used in many cases. For example, an interlayer insulating layer can be formed using silicon oxide which is an inorganic material containing silicon. For the above reason, a low dielectric constant is required for an interlayer insulating layer, and as one of methods for realizing a low dielectric constant, proposed is a method for adding fluorine to an insulating layer (for example, Patent Document 1: Japanese Published Patent Application No. H8-236519).
As described above, by adding fluorine to an insulating layer, a dielectric constant can be reduced, but there occurs a problem that the insulating layer absorbs moisture more easily than an insulating layer to which fluorine is not added. Further, when fluorine and water in the insulating layer react with each other, there also occurs a problem that the insulating layer is porous and thus a dielectric strength voltage and mechanical strength are reduced.